Well, if you intend to make any slightly larger games, won't you need to include some kind of memory mapper? How complicated will something like that be?
Not just a mapper (which is available in chip form), but also a decoder for the address lines, so you don't 'accidentally' change the mapper registers.
Which also implies you lose some space from the chip, though you could probably map the mapper into the i/o page fairly easily....
But seriously: 8M bit = 1M byte = one big game. Even bigger if you compress stuff, and decompress it when needed.
Your biggest problem with a 8M bit+ game is gonna be powering it all.....
